Decadal brightening in the northeastern non-thermal filament of Cassiopeia A

TL;DR

This study documents a decade-long increase in non-thermal emission from a filament in Cassiopeia A, revealing complex shock interactions and particle acceleration processes in a young supernova remnant.

Contribution

It provides the first detailed decadal analysis of non-thermal flux evolution and morphological changes in Cassiopeia A's northeastern filament, highlighting nonlinear shock and magnetic effects.

Findings

Non-thermal flux increased by tens of percent since 2000.

Filament split into two sections with contrasting behaviors.

Spectral shape remained largely unchanged over two decades.

Abstract

We present the decadal brightening of non-thermal emission flux in the northeastern filament of the young supernova remnant Cassiopeia A (Cas A), which highlights dynamic processes in the forward shock. This filament, characterized by the highest particle acceleration rate among Cas A's outer shells, offers an exceptional opportunity to investigate underlying astrophysical mechanisms. Since 2000, the non-thermal flux has increased by several tens of percent before plateauing, while the spectral shape has remained largely unchanged. Over the past two decades, the filament's morphology has evolved significantly, splitting into two distinct sections. Detailed analysis reveals contrasting behaviors: one section shows a flux increase followed by saturation, while the other maintains a steady flux. These differences likely arise from nonlinear effects, including magnetohydrodynamic interactions influenced by magnetic field orientation, interactions with surrounding material, and complex fluid dynamics associated with young supernova remnants. The localized evolution of this filament, captured with high spatial resolution, provides critical insights into the temporal dynamics of non-thermal particles and the generation of cosmic rays from asymmetric supernova explosions.